MORPHOLOGY AND EVOLUTION
(4) Deep facial rein (D.F.Y. .
(5) SulmaxiUarif win (S.JLGO.
(6) Lingual vein* (L.V.*.
(7) Laryngeo-thj/roid trunk sL.T.V.,).
(8) Pharyngeal reins (Ph. V.,».
The anterior facial veins are not united by a transverse vein as in many other lower animals, and there is no anterior jugular vein. In the Orang the laryngeal, thyroid and pharyngeal veins enter the internal jugular vein.
The temporo-maxillary vein in the Chimpanzee ifig. 45, T.M.V.) is formed within the parotid gland by the union of superficial temporal (S.T.V.) and internal maxillary veins. It receives the short internal jugular vein iI.J.V.) and unites with the anterior facial vein to forru
the external jugular vein. Its transverse facial tributary is well marked.
The external jugular vein (E.J.Y.) crosses the surface of the sterno-mastoid in the Gorilla (Bisler), but it always passes deep to the muscle in the Chimpanzee. At the outer border of the first rib it unites with the sub-clavian vein to form the innominate vein in the Chimpanzees but it enters the junction of the internal jugular and subclavian veins in the Gorilla and Orang.
The internal jugular vein in the Gorilla and Orang is much as in Man. In the Chimpanzee it passes into the temporo-maxillary vein high up in the neck.
Veins of the Thorax.
In the Chimpanzee (fig. 45, B.), the left innominate vein runs obliquely; it receives inferior thyroid (I.T.V.), thyrnic, internal mammary (I.M.V.), and superior